Effect of Bacteria and Mechanical Loading on Degradation of the Composite-Tooth I

描述(由申请人提供)：本申请代表多学科、多机构对RFA-DE-10-004：延长牙科树脂复合材料的使用寿命(R01)的回应。更换牙科复合体的主要原因是龋病和骨折。虽然两者背后的机制都不清楚，但大多数失败前几年的时间进程表明，材料/牙齿界面和/或材料的某些降解过程发生在口腔环境中。我们的总体目标是进一步阐明牙科复合修复体周围细菌反复引起牙齿结构脱矿的机制，并开发抑制这种脱矿的方法。为此，我们将通过改变界面间隙的起始大小以及树脂复合材料的固化程度来确定细菌在牙科复合修复剂和牙齿结构之间定植的条件。我们进一步打算评估在循环载荷下接触细菌对边缘界面的影响。本研究要检验的一个中心假设是，存在一个有限的界面间隙大小，这使得复合修复界面易于被细菌定植和广泛的脱矿，并且该界面可能会因细菌的影响而进一步退化。我们还打算将一种新型的生物活性玻璃(BAG)加入到树脂复合材料中，以开发一种新的牙科修复材料。我们的假设是，当长期暴露在疲劳载荷和口腔生物膜形成的组合下时，与没有抗菌生物活性玻璃的材料相比，带有BAG的材料以及这些材料与牙齿结构之间的界面经历的化学和机械降解较少。为了进一步探讨失败的机制，通过生产不同固化程度的树脂，材料的抗微生物行为将有所不同，这可能反映了牙科复合材料在临床实践中产生的高度不同的结果。材料将被放入牙齿中的制剂中，在界面间歇疲劳加载之前和期间，将在其表面生长生物膜。界面失效和细菌的存在将通过光学和扫描电子显微镜进行评估。脱矿的证据将通过能谱(EDS)x射线分析来确定。通过表面分析，包括光泽度、表面粗糙度和显微硬度，将评估带和不带袋子的复合材料上生物膜效应的证据。这项应用对RFA规定的范围中的三个方面特别敏感，包括开发新的材料来提供防龋性，确定边缘间隙大小是否对细菌定植和进一步脱矿有影响，以及在临床相关环境中阐明修复材料失效的机制。这项工作的潜在有益结果是，由于更持久的牙科树脂复合修复体，在美国(和全球)广泛节省了口腔保健成本，并减少了口腔疼痛。 公共卫生相关性：更换牙科复合材料的主要原因是牙齿进一步腐烂。我们的总体目标是更好地了解当口腔细菌和机械应力暴露时，使用牙科复合材料修复的牙齿中复发空洞的形成机制。此外，我们打算展示包含新型生物活性玻璃的新的牙科复合配方可以使修复更好地抵抗模拟口腔环境中细菌的负面影响。这项工作的结果可能是延长牙科复合修复体的寿命和使用寿命，从而节省患者进一步的痛苦、金钱和牙科治疗。

DESCRIPTION (provided by applicant): This application represents a multidisciplinary, multi-institution response to RFA-DE-10-004: Increasing the Service Life of Dental Resin Composites (R01). The primary reasons for replacement of dental composites are caries and fracture. Whereas the mechanisms underlying both are ill-defined, the time course of years preceding most failures suggests that some process of degradation of the material/tooth interface and/or material occurs within the oral environment. Our overall goal is to further elucidate the mechanism of recurrent demineralization of tooth structure by bacteria around dental composite restorations, and to develop solutions for inhibiting it. To do this, we will identify conditions under which bacteria colonize interfaces between dental composite restoratives and tooth structure, by varying the starting size of the interfacial gap as well as the extent of cure of the resin composite. We further intend to evaluate the effect of the exposure to bacteria under cyclic loading on the marginal interface. A central hypothesis to be tested in this study is that there is a finite interfacial gap size that predisposes the composite restorative interface to colonization by bacteria and extensive demineralization, and that this interface may be further degraded by the effects of the bacteria. We also intend to incorporate a novel bioactive glass (BAG) into the resin composite to develop a new dental restorative material. Our hypothesis is that materials with BAG, and the interface between these materials and tooth structure, will undergo less chemical and mechanical degradation than those without an antibacterial bioactive glass when exposed to a combination of fatigue loading and oral-type biofilm formation for extended periods of time. To further probe the mechanism of failure, the anti-microbial behavior of the materials will be varied by producing resins with different extents of cure, which likely reflects the highly variable outcomes produced for dental composites in clinical practice. Materials will be placed into preparations in teeth and biofilms will be grown on their surface before and during intermittent fatigue loading of the interface. Interfacial failure and bacterial presence will be assessed by optical and scanning electron microscopy. Evidence of demineralization will be determined by energy dispersive spectroscopic (EDS) x-ray analysis. Evidence for biofilm effects on composites with and without BAG will be assessed by surface analysis, including gloss, surface roughness and microhardness. This application is particularly responsive to three aspects of the defined scope of the RFA, including development of new materials to confer caries resistance, determining whether the marginal gap size has an effect on bacterial colonization and further demineralization, and elucidating mechanisms of restorative material failure in a clinically relevant environment. The potential beneficial outcome of this work is extensive cost savings in oral health care and reduced oral pain in the US (and globally) due to longer lasting dental resin composite restorations. PUBLIC HEALTH RELEVANCE: The primary reason for replacement of dental composites is further decay of the tooth. Our overall goal is to better understand the mechanism of recurring cavity formation in teeth restored with dental composites when they are exposed to oral bacteria and mechanical stress. Further, we intend to show that new dental composite formulations containing novel bioactive glasses can render the restoration more resistant to the negative effects of bacteria in a simulated oral environment. The outcome of this work may be increased longevity and service life of dental composite restorations, thus saving the patient further pain, money and dental treatment.